1. Field of the Invention
The present invention relates to a multi-scanning control process and LED display board utilizing the multi-scanning control process. More particularly, multi-scanning control is performed by sequentially overlapping horizontally and vertically neighboring LEDs of pixel units to intensify the resolution rate per pixel unit through a multi-scan card, a receiver board and pixel drivers.
2. Related Prior Art
Generally, an electric displaying device (201) is assembled with a plurality of LED modules (202), basic LED panels (203) and pixel units (204) to have appropriate brightness (a minimum of 5,000 to a maximum of 8,000 cd/m2 for an outdoor screen, and a minimum of 1,000 to a maximum of 3,000 cd/m2 for an indoor screen) at a fixed pitch (generally 10 mm, 12.5 mm, 14 mm, 15 mm, 16 mm, 20 mm, etc.). The pixel units (204) consist of three primary colors—red, green and blue LEDs. A LED panel (203) having a plurality of pixel units (204) is the basic unit for assembling the electric displaying device (201). Furthermore, a plurality of LED panels (203) is fabricated to form a LED module (202), so that it is convenient to assemble the final screen (201). As seen in FIG. 2, a typical screen (201) displaying an image with a resolution of 320×224 is assembled from a plurality of LED modules (202) with a resolution of 32×32, basic LED panels (203) with a resolution of 16×8, and pixel units (204) formed from a set of LEDs. In the case of the exemplary screen, the pixel unit is formed from two red LEDs, one green LED and one blue LED.
Usually, an electric displaying device utilizing a conventional single-scanning process emits a pre-set resolution fixed by the screen size. As seen in FIG. 1, all LED panels of 8×8 (101), 16×8 (102), 16×16 (103) and 32×16 (104) have the same resolution rate per pixel unit due to the single-scanning process. The brightness and resolution of each panel is proportionate to the size and area of the pixel panel. That is, the brightness and resolution of a conventional screen is fixed at the manufacturing stage by the size of the pixel panel. In other words, when a pixel unit (204) is represented as a dot, the resolution rate per pixel unit or dot rate per unit size and area of pixel panel is 1:1. Therefore, the resolution rate per pixel unit of each 8×8 LED panel (101), 16×8 LED panel (102), 16×16 LED panel (103) and 32×16 LED panel (104) is the same, and the overall resolution is proportionate to the size and area of each LED panel. The various arrangements (105) of LED pixels are presented as examples.
Generally, a basic LED panel (203) has a size of 16×8 resolution. Therefore, an LED module (202) of 32×32 resolution is fabricated with eight basic LED panels (width 2×length 4). Usually, 70 LED modules (width 10×length 7) are required to produce a screen (201) of 320×224 resolution. That is, 560 basic LED panels (width 20×length 28) or 71,680 pixel units or dots (width 320×length 224) are required to produce a screen.
Although conventional technology may satisfy the required screen resolution, it has a technical limitation due the fixed resolution rate per pixel unit. If a high-resolution screen is required, the screen size should be increased to meet the requirement. To accomplish this, however, the number of basic LED panels must be increased, which therefore raises the product cost. Furthermore, the source of image data and the control signal, as well as the capacities of the controlling device, should be increased as the screen size is increased in order to meet the optimum resolution and displaying condition.
As shown in FIGS. 1e, 3a and 3b, the various arrangements of LEDs for the pixel unit are introduced. For example, a pixel unit adopting two yellow-green LEDs is arranged within a lozenge shape, as seen in FIG. 3a. A pixel unit adopting a pure green LED is arranged within a triangle shape, as seen in FIG. 3b. Usually, a pitch of 12.5 mm is used for arranging the LEDs in the pixel unit of the conventional single-scanning method.
The pixel unit of the conventional method has limited resolution due to the fixed size and number of LEDs in the pixel unit. Because of limited resolution, the conventional screen is for outdoor use, which requires more than 15 m of visual distance. Generally, the conventional screen is not suitable for indoor use, which requires high resolution.
A PDP as a displaying device used for advertisement has 600 cd/m2 of illumination and 5000 hours of lifespan. A projector has 1000 cd/m2 of illumination and 3000 hours of lifespan. Contrarily, an electric displaying board configured with four LEDs per pixel unit has 5000 cd/m2 of illumination and 50,000 hours of lifespan. Although the LED displaying board has the great advantages of high illumination and long lifespan, it cannot be applied to an indoor screen due to the requirements of short visual distance, high resolution rate and high production cost.
Referring to FIG. 5a and FIGS. 6 through 8, an operation of the conventional single-scanning process is disclosed along with the configuration of the pixel unit, the signal flow of a single-scan card, receiver board and pixel driver.
The conventional single-scanning process has a 1:1 resolution rate per pixel unit. The conventional processor equips a control board comprising a scan card, a receiver board and a pixel driver board for controlling the RGB LEDs. Although more than one same color LED exists in the conventional pixel unit, the same color LEDs are connected in parallel to a common pixel driver, as seen in FIG. 8. That is, the red LED is connected to the red pixel driver. Two green LEDs are connected in parallel to a common green pixel driver. The blue LED is connected to the blue pixel driver. So, the common green pixel driver controls two green LEDs, at the same time.
Referring to FIG. 6, the single-scan card (60) of the conventional process receives an RGB signal and control signal from the control PC and distributes the received control signal, RIG data and G/B data to each receiver board (70). The single-scan card (60) comprises a video memory (61), a data latch circuit (62), an RS-422 data converter (63), a clock generator (64), a synchronizing signal generator (65) and a control signal generator (66).
Referring to FIG. 7, a conventional single-scan receiver board (70) receives the control signal, R/G data and G/B data from the single-scan card (60). The scan receiver board (70) comprises a TTL data converter (71) for converting the digital signal to TTL data, a display memory (74) for storing the RGB signal, an address generator (72) for accessing the control data, a data latch circuit (75), a display signal generator (73) for addressing and clocking the data, a serial signal converter (76) for converting the data to a serial signal, a data converter (77) for converting the serial signal to a parallel signal, and an output buffer (78) for outputting the data to the pixel driver block.